Taps, or knocks, are commonly used to attract attention. It is one form of informal communication. In different cultures, tapping or knocking can share the same meaning. For instance, both in Eastern or Western countries, it is polite for one to tap on the door to seek approval before entering a room. The taps signify the person's intention of entering the room and also arouse attention amongst those inside the room to address this intent.
In Chinese culture over meals, there is a convention for one to gently tap on the table with his knuckles continuously when another person is filing his/her cup with tea. This knuckling gesture conveys appreciation and gratitude to the other person, and is believed to have come from a legend that once there was a King disguised in peasant wear to informally cruise his country, and who was at meal with his liegeman, serving tea to one of them. The liegeman should have knelt on the ground and bowed his head to receive this divine treatment from the King. In order not to reveal his royal status, the King signaled the liegeman to tap on the table with knuckles of his bent fingers in place of the kneeling and bowing. In addition to common causal communication, tapping could also be used to communicate more specific information. In particular, a tapping sequence specifically constructed (e.g. with specific intervals in between taps) could be used to represent or “encode” a particular piece of information or message. For example, children in particular, like to create secret codes by special knocking patterns on the door to identify friends from strangers. This code is simply composed by a sequence of knocks that follows some kind of rhythm. In principle, this can also be explained as the distribution of knocks within a certain time. By varying the time intervals in between knocks, different rhythms of knock sequences can be created.
Finally, tapping is also one form of physical externalization of thoughts and emotions. Since taps already exist as an informal form of communication, it offers good potentials in building upon on this common and natural human gesture to developing intuitive interfaces to digital devices. There is the possibility of exploiting both the rhythm (“time-based”) and/or the path (“position-based”) of a tap sequence for system manipulation. Tangible User Interface (TUI) that makes use of tapping as an input method can simplify the control of many existing systems. It offers an elegant, simple, and natural form of interaction.
In order to maximize the diversity in application as well as the interactivity between the system and user, the interactive system would be desirable to be able to recognize both the rhythm (“time-based”) and the path (“position-based”) of knock sequence efficiently and precisely.
The prior art has shown sound-sensitive interactive surface. The Passive Acoustic Tap Tracking Across Large Interactive Surface is a system that locates the position of knocks and taps atop a large sheet of glass surface. Microphones embedded at four corners of the sheet glass are used to find the position of knocks of the surface. By calculating and comparing the time that sound waves travel from where the knock occurs to the four microphones on the surface, position of the knock on the surface can be measured. Unfortunately, this method of tracking position of taps on a surface has an accuracy problem. It has been shown that such a system is not able to resolve knocks that are spaced less that 10 cm apart, and so the system was inaccurate in tracking the path (“position based”) of knocks with this range.
It is an object of the present invention to overcome the disadvantages and problems in the prior art by providing a new acoustic sensitive interactive surface.